The present invention relates to a conveyor system for removing debris, trash, and similar material from a moving body of water such as in a sewage treatment plant. More particularly, the invention is directed to a new and improved rake member for installation on a conveyor which is constructed of a tough, highly abrasion- and corrosion-resistant elastomer.
Mechanically raked bar screens are used in a variety of circumstances, for example in the treatment of sewage to remove suspended solids from a flow of liquid. Such screens comprise a series of parallel grating bars which extend across the channel, duct, or other opening carrying the liquid, the bars being preferably upwardly inclined in a vertical plane. The teeth of rake members carried by an endless conveyor project through the grating bars, and as the endless belt is continuously rotated debris or the like is cleared from the inner face of the bar screen and carried by the rake teeth. The backing portion of the rake which carries the teeth rides against the grating bars as the rake is carried upward to deposit the collected debris or the like at the top of the conveyor. The configuration of the bar screen and the conveyor system varies. For example, the bars may be aligned either vertically or obliquely to the vertical or they may be curved, in which case they will generally be arranged with their concave sides facing upstream of the flow of liquid to be screened. Regardless of the nature of the construction, however, the teeth of the rake must pass through the bars in close-fitting relation in order to remove all of the debris, including finely divided debris.
In the construction of the mechanically raked bar screens, the bars have been constructed of steel rods, spaced apart and welded; and the rake has been similarly constructed of a metal such as steel. Heretofore it was believed essential that the rakes, including the teeth of the rakes, be constructed of steel or other heavy metal in order to ensure the necessary durability and carrying strength. The construction of the rakes from metal was with the recognition of the problems which occur when the teeth of the rakes do not align exactly so as to pass between the spaced parallel bars, which leads to a jamming of the teeth into and against the bars. Since the jamming or damage usually occurs at the point of alignment of the teeth and bars which is below the surface of the stream of liquid being treated, resolution of the jamming problem necessitates closing down the operation and, more often than not, the emptying of the liquid being treated from the channel to permit replacement or repair of the rakes. Further, the metal rakes, because of the corrosive nature of the effluent carried particularly in sewage treatment plants and the riding of the backing member of the rake against the bars, have only a limited life.